Light projection systems used for such purposes as spotlights for theatrical situations such as stage productions and concerts are not adaptable for use in the type of varied light displays required as decorative backgrounds for such environments as popular music concerts or nightclubs. Such decorative displays are intended to create a general illusion or effect rather than to systematically illuminate performers or objects. The light display systems being used are generally projections of a single light beam that is moved in a single projection pattern.
Light beams used to decorate an area are known. The simplest type uses a single mirror that generally is rotated about a single vertical axis. The optical integrity of a single mirror system is limited because to get a constantly moving pattern the mirror must be tilted almost parallel to the incoming rays with the result that some rays will bypass the mirror entirely, which bypassing rays will not rotate but will be stationary, so that the whole moving decorative effect is spoiled.
Another decorative lighting system is known by the trade name of Vari-Lite. This system is described in U.S. Pat. No. 4,392,185. Although a continuously moving light covering substantially a full spheroid by using simultaneous pivotal movement of the light beam over an X-Y axis is achieved, the system is flawed in that the entire luminaire containing the lamp, iris, lens, shutter, color changer, dimmer, and special effects pattern device. The resulting inertial problems of revolving this mass, including power, operational, and cost problems of this system, are not to be minimized.